Cura marketplace is a collection of plug ins and filament profiles to work with cura to enhance your user experience, To access the marketplace start cura and press the marketplace button at the top right hand corner.
You will then be greeted with the menu for the plugins and filament profiles, To use these click the install button and restart cura.
Handy plugins are the settings plugin which will give you a read up on what the particular setting does and what other settings it affects.
The auto towers plugin will produce calibration towers to calibrate you printer and filaments.
The moonraker connections plugin will allow you to send the sliced files straight to your klipper printer via your home network.
The octoprint connection plugin does the same as the moonraker plugin for users that have octoprint.
The power cost plugin will estimate how much the power will cost to print that model.
Material cost tools will estimate how much filament a model will use and what the filament cost is for that model.
Thingibrowser will allow you to search thingiverse and import the model straight into the slicer.
Simply click on the details tab to get the models details.
Select the model you like and click add to build plate.
Orientate the model on your build plate so that the model shows as little red as possible, red means its unsupported and requires supports.
Click the model on the build plate and the menu on the left will become active, select the third icon down that looks like a arrow going backward, at this point you will get 3 coloured circular arrows around the model that you can use to orient the model.
Once you are happy with the orientation hit the slice button, Then sent over moonraker/octoprint or write to your sd card.